首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   22473篇
  免费   2791篇
  国内免费   1439篇
电工技术   1678篇
综合类   2293篇
化学工业   1557篇
金属工艺   363篇
机械仪表   1236篇
建筑科学   3452篇
矿业工程   4196篇
能源动力   711篇
轻工业   304篇
水利工程   756篇
石油天然气   534篇
武器工业   423篇
无线电   1509篇
一般工业技术   1178篇
冶金工业   895篇
原子能技术   98篇
自动化技术   5520篇
  2024年   65篇
  2023年   256篇
  2022年   631篇
  2021年   836篇
  2020年   891篇
  2019年   646篇
  2018年   586篇
  2017年   714篇
  2016年   864篇
  2015年   947篇
  2014年   1783篇
  2013年   1419篇
  2012年   2066篇
  2011年   2106篇
  2010年   1661篇
  2009年   1578篇
  2008年   1564篇
  2007年   1673篇
  2006年   1328篇
  2005年   1077篇
  2004年   840篇
  2003年   727篇
  2002年   560篇
  2001年   401篇
  2000年   304篇
  1999年   217篇
  1998年   178篇
  1997年   156篇
  1996年   134篇
  1995年   97篇
  1994年   119篇
  1993年   54篇
  1992年   37篇
  1991年   36篇
  1990年   29篇
  1989年   23篇
  1988年   19篇
  1987年   9篇
  1986年   9篇
  1985年   12篇
  1984年   11篇
  1983年   6篇
  1982年   4篇
  1979年   4篇
  1970年   3篇
  1964年   2篇
  1960年   2篇
  1959年   2篇
  1957年   2篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Melt index is considered an important quality variable determining product specifications. Reliable prediction of melt index (MI) is crucial in quality control of practical propylene polymerization processes. In this paper a least squares support vector machines (LS‐SVM) soft‐sensor model of propylene polymerization process is developed to infer the MI of polypropylene from other process variables. Considering the use of a SSE cost function without regularization might lead to less robust estimates; the weighted least squares support vector machines (weighted LS‐SVM) approach of propylene polymerization process is further proposed to obtain a robust estimation of melt index. The performance of standard SVM model is taken as a basis of comparison. A detailed comparison research among the standard SVM, LS‐SVM, and weighted LS‐SVM models is carried out. The research results confirm the effectiveness of the presented methods. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 285–289, 2006  相似文献   
62.
Carbon black composites (CBCs) have been prepared by pyrolyzing mixture of a carbon black with polyfurfuryl alcohol and then pretreated by oxidation with nitric acid, gasification with water steam or ammoxidation. The effects of the chemical character of the carrier surface, nature of the active metal phase and pH value of the impregnation solution on the catalytic activity towards the hydrodesulfurization (HDS) of thiophene of the CBC supported Mo (Co) catalysts were determined. It was stated that the catalytic properties of the CBC supported sulfides of Mo or Co and of Mo carbides are affected by the chemical character of the carrier surface. Generally, catalysts supported over basic surface CBC exhibit higher activity than those ones supported over CBC possessing acidic surface character. Co catalysts supported on acidic surface show lower activity (per mol of active metal) than Mo based ones supported on the same carrier. In the case of catalysts supported on basic CBC, Co exhibits distinctly higher activity than Mo. At the experimental conditions adopted for this study, CBC surface properties, active phase nature, and catalyst impregnation pH were found to exert a relatively small influence on both HDS and hydrogenation activities.  相似文献   
63.
Maintenance strategy based on a multicriterion classification of equipments   总被引:4,自引:0,他引:4  
In an industrial plant, the level of maintenance provided to individual equipment is directly related to the availability that is expected from it. Thus, it is hoped that the most critical equipments will not fail or, at least, that any failure will be rapidly detected and corrected in the minimum time possible. Since resources are limited, it is necessary to determine how they should be distributed, so that no important equipment remains neglected while more resources are concentrated on the most critical items. Therefore, it is necessary to classify equipment in an objective way according to its importance. The method of multicriterion classification of critical equipments (MCCE)2, which is described in the present work, allows systematic and detailed quantification of the criticality of all equipment, that is to say, it provides an evaluation of the importance that its correct operation has for the plant. To provide this information, the consequences for a company of any failure in the equipment concerned are analysed. Finally, a real case example of an urban wastewater treatment plant is described, in which the MCCE method is applied.  相似文献   
64.
胡德春 《大坝与安全》2007,(1):49-51,56
混凝土喷锚支护可提高边坡岩土的结构强度和抗变形刚度,增强边坡的整体稳定性和承载能力.本文根据宝珠寺水电站左右岸边坡主要采用混凝土喷锚支护的工程实践,介绍了施工方案设计、材料要求、施工方法、技术措施,以及现场质量管理和检测等问题.  相似文献   
65.
超化煤矿21091(西)综采工作面因出水造成工作面停产,在不超前15 m铺金属网的情况下进行支架拆除,并把原工作面留做炮采面切巷。根据实际情况制定了施工方案,并介绍了实施情况。  相似文献   
66.
Complementary foods based on cereals and legumes often contain high amounts of phytic acid, a potent inhibitor of mineral and trace element absorption. The possibility to degrade phytic acid during the production of complementary foods by using whole grain cereals as the phytase source was investigated. Whole grain rye, wheat, or buckwheat (10%) were added to cereal‐legume‐based complementary food mixtures, and phytic acid was shown to be completely degraded in a relatively short time (1.5 to 3 h) when incubated at optimal conditions for cereal phytase. The potential usefulness of the method for industrial production was demonstrated with a complementary food based on wheat and soybean.  相似文献   
67.
Comments on the article by K. T. Herbst-Damm and J. A. Kulik (see record 2005-02260-012) entitled Volunteer support, marital status, and the survival times of terminally ill patients. Can a simple and low-cost intervention, such as a visit by a volunteer, extend the life of terminally ill patients? The answer, according to a study by Herbst-Damm and Kulik (2005), is yes. When it comes to quality of life, however, the effects of volunteer visits remain murky. Thus, it is critical that we look beyond effects on longevity and assess how such a program would influence quality of life. Extending the life of terminally ill patients might not always a blessing. Prolonging their life might even cause harm, as it can extend unwanted physical and mental suffering. It may also go against some patients' desire to hasten their death. Despite Herbst-Damm and Kulik's important findings, the current author remains unconvinced as to the merits of implementing volunteer visits as an intervention policy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
68.
新庄孜煤矿在总结各类支护型式优缺点的基础上 ,大力推广应用锚注支护技术 ,先后在修复高应力软岩冒落架棚巷道、修复砌碹巷道、修复大断面峒室等施工中灵活使用锚注支护技术 ,均取得良好的支护效果和显著的技术经济效益  相似文献   
69.
Global competition, commitment to the Kyoto Protocol and a deregulated, integrated European electricity market will in all probability increase the demand for energy efficiency on the part of companies in Sweden. Investment decisions are an important part of meeting the new demands, because they decide the future efficiency of industrial energy systems. The objective of this study is to investigate, from a managerial perspective, the need to improve decision support in some industries, which can help to facilitate and improve investment decisions concerning energy efficiency. This work has been conducted through in-depth interviews with representatives for a number of energy-intensive companies and non-energy-intensive companies from different sectors. One need that was identified was the improvement of working methods in order to support the decision-making process. Here, external players seem to be playing an increasingly important role. Access to correct information, better follow-up activities, and transparent, understandable calculations are also considered to be important. The study will form the foundation for subsequent work on decision support and energy efficiency in industry.  相似文献   
70.
地下连续墙在太钢老厂改造工程中的应用   总被引:1,自引:1,他引:0  
闫兴旺 《山西建筑》2003,29(3):75-76
结合某深基坑支护施工实例 ,介绍了采用多头潜水钻成槽机进行地下连续墙施工的基本原理、工艺流程及注意事项。指出该方案对于在老厂区改造工程狭窄场地条件下 ,解决深基坑施工保护附近建 (构 )筑物安全具有独特的优势  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号